Hypothesis for development of a behavioral phenotype in Williams syndrome.

We investigated the natural history of Williams syndrome (WS), including physical characteristics and cognitive, academic language, sensory integration, and adaptive and maladaptive behavior in 32 patients (age 3 to 30 years). These patients were available for psychoeducational testing, parent interview, medical and educational record review, and behavioral observation. Thirty-seven nonlocal individuals (age 8 months to 31 years) were not tested but data on history and development, sensory integration, adaptive and maladaptive behavior were collected resulting in a total sample of 69. The unique constellation of physical manifestations and associated clinical problems in WS contributes to a characteristic behavioral phenotype of 6 factors beginning in infancy with development of salient attachment behaviors. Later a key issue affecting the learning abilities of both the school-aged child and adult with WS was an inadequate development in the use of tools. Theoretical constructs from developmental behavioral genetics, attachment theory, operant conditioning, neuropsychology, and psychosocial theory considered interactively offer explanations for these characteristics.